michelle asked
Oxycontin 20 mg extended release... How many milligrams per hour am I getting?
Answer
Oxycontin (oxycodone extended release) tablets have a "biphasic" release mechanism (trademarked AcroContin) and do not release consistent levels of oxycodone while the tablets are being metabolized by the body. Therefore, it is difficult to definitively state how many milligrams are being released at any given point from an Oxycontin tablet.
Once ingested, the first layer of the Oxycontin tablet dissolves in the stomach/GI tract, delivering an "immediate release" dose of oxycodone within one hour. Studies put the initial amount of oxycodone released at about 40% of the total oxycodone contained in the tablet. From there, the tablet continues to slowly deliver oxycodone over a period of 12 hours as it moves through the GI tract.
Although the release of oxycodone from Oxycontin tablets is variable, studies have shown that there is a predictable "dose proportionality" across all Oxycontin tablet strengths (10 mg, 15 mg, 20 mg, 40 mg, and 80 mg) in regard to both peak plasma concentrations reached and the total extent of absorption.
For example, studies have shown the following:
- 10 mg of OxyContin every 12 hours is considered equivalent (in terms of average concentration and the maximum concentration reached in the body) to 5 mg of immediate-release oxycodone every 6 hours.
- 20 mg of OxyContin every 12 hours is considered equivalent (in terms of average concentration and the maximum concentration reached in the body) to 10 mg of immediate-release oxycodone every 6 hours.
- 40 mg of OxyContin every 12 hours is considered equivalent (in terms of average concentration and the maximum concentration reached in the body) to 20 mg of immediate-release oxycodone every 6 hours.
- 80 mg of OxyContin every 12 hours is considered equivalent (in terms of average concentration and the maximum concentration reached in the body) to 40 mg of immediate-release oxycodone every 6 hours.
The following chart from the Oxycontin package insert, confirms the dose proportionality described above. 10 mg of Oxycontin, dosed every 12 hours, reaches the same (or very similar) average concentrations (AUC) and maximum concentrations (Cmax) as 5 mg of oxycodone dosed every 6 hours. The only difference is time to maximum concentration. Immediate release oxycodone tablets reach maximum concentrations faster.
Summary
Oxycontin tablets are biphasic. When taken by mouth, part of the total dose is released immediately (about 40% of the total dose). The rest of the oxycodone contained in the tablet is released slowly over a 12-hour period. Due to this release mechanism, it is not possible to determine how many milligrams per hour are released. However, Oxycontin tablets are dose proportional to immediate release tablets, as described above.
